The scorching destruction of Australia’s Black Summer bushfires between 2019 and 2020 gave an ominous glimpse of the reach of fire in our hotter, drier world, and the impact of the unprecedented inferno is still being measured.
Just a few weeks ago, scientists noted that the amount of smoke spewed into the atmosphere by the flames rivaled that of a major volcanic eruption. Now researchers say the giant cloud of smoke was so immense that it measurably heated the stratosphere for months.
In a new study led by first author and climate modeller Pengfei Yu of China’s Jinan University, scientists simulated the rise and evolution of the plume, showing that the worst documented wildfires in Australian history had a lasting impact on the air in the region.
“Extreme wildfires can inject smoke into the upper troposphere and even into the stratosphere under favorable meteorological conditions,” the researchers write in their paper. “The higher the smoke is injected, the longer it will last and the greater the size.”
In the case of the Black Summer fires, the flames sent nearly a trillion grams (about 0.9 teragrams) of smoke particles into the stratosphere, which the researchers say is the largest amount ever documented in the satellite era.
This smoke mass consisted of different types of smoke particles, including both organic carbon (OC, including brown carbon, also known as BrC), and black carbon (BC).
Each of these has different heat-trapping effects in the atmosphere, with BC trapping the most heat, due to the way it warms the surrounding air after absorbing sunlight.
According to the researchers’ calculations, the Black Summer plume was about 2.5 percent black carbon, which caused a heating effect in the stratosphere for the rest of the year.
“Simulations suggest that the smoke remained in the stratosphere throughout 2020 and that it measurably warmed the stratosphere by about 1-2 K [Kelvin, equivalent here to 1-2 degrees Celsius] more than six months’, the team explains.
“Our study highlights that record-breaking wildfire smoke can have lasting effects on stratospheric dynamics and chemistry.”
In addition to warming up the stratosphere, the researchers say the record-breaking smoke event would also have had a diminishing effect on stratospheric ozone levels, destroying ozone molecules in the mid-latitudes of the Southern Hemisphere and likely creating the ozone hole. temporarily bigger.
While the researchers acknowledge that there have been previous observations of aerosols causing stratospheric warming, it is the first time that scientists have measured the phenomenon like this, given the record-breaking output of the Black Summer fires.
The findings are reported in Geophysical Research Letters